Kane gets a "free pass" because of the versatility of his character. His willingness to keep on with WWE for damn near two decades through all of the bullshit gimmicks he's had to endure. Kane puts people over in a second, cleanly. Kane would go out there in a thong and job more than Tensai if it meant helping the company.

Meanwhile Cena throws his hissy fits on twitter if he even imagines that he might just possibly take a backseat to someone. He no sells matches and injuries, his gimmick isn't worth wiping with. Cena hasn't and probably never will do any of what Kane's done because he's simply not that talented or willing to.